This invention relates to detection of a small speed ratio of a toroidal continuously variable transmission for vehicles on startup.
Tokkai Hei 7-4508 published by the Japanese Patent Office in 1995 discloses a toroidal continuously variable transmission for vehicles.
This toroidal continuously variable transmission varies a speed ratio by varying a gyration angle of power rollers gripped between an input disk and an output disk.
The gyration angle variation of the power rollers is performed by driving trunnions which support the power rollers in a perpendicular direction to a rotation shaft of the input disk.
For this purpose, an oil pressure cylinder, which is actuated by discharge oil of an oil pump driven by the engine. is attached to each of the trunnions.
When the vehicle runs while the engine is stopped, that is, when the vehicle goes down a slope due to an action of gravity. or when the vehicle is towed, for example, the rotation torque of the driving wheels is transmitted to the input disk via the power rollers from the output disk in the toroidal continuously variable transmission.
In connection with the transmission of this torque, the gyration angle of the power rollers vary in a direction which makes the speed ratio small.
Therefore, if the engine is started to start the vehicle after the vehicle has stopped, as the speed ratio is small, the torque required for startup cannot be immediately obtained. So, the toroidal continuously variable transmission largely varies the speed ratio so that the large speed ratio required for vehicle startup can be realized.
The torque increases rapidly due to this sharp variation of the speed ratio. That is, the startup of the vehicle is dull at first, but the vehicle then dashes forward abruptly, and the driver will have an uncomfortable feeling.
It is therefore an object of this invention to inform the driver promptly if a vehicle starts up when the speed ratio of a toroidal continuously variable transmission is small.
It is a further object of this invention to start the vehicle smoothly even when the speed ratio of the toroidal continuously variable transmission is small.
It is still a further object of this invention to detect the gyration angle of the power rollers precisely by a simple construction.
In order to achieve the above objects, this invention provides a detecting device of speed ratio of a vehicle. The vehicle is provided with a toroidal continuously variable transmission joined to an engine and an ignition switch for starting operation of the engine. The detecting device comprises a sensor which detects that a speed ratio of the toroidal continuously variable transmission is smaller than a predetermined speed ratio range including a maximum speed ratio, and a microprocessor programmed to determine whether or not the ignition switch is in a starting position of the engine, and determine that the vehicle is starting under a small speed ratio, when the ignition switch is in a starting position of the engine and the speed ratio of the toroidal continuously variable transmission is smaller than the predetermined speed ratio range.
It is preferable that the vehicle is further provided with a warning device and the microprocessor is further programmed to turn on the warning device when it is determined that the vehicle is starting under a small speed ratio.
This invention also provides a control device for a toroidal continuously variable transmission joined to an engine of a vehicle. The vehicle is provided with an ignition switch for starting operation of the engine. The control device comprises a sensor which detects that a speed ratio of the toroidal continuously variable transmission is smaller than a predetermined speed ratio range including a maximum speed ratio, and a microprocessor programmed to determine whether or not the ignition switch is in a starting position of the engine. and control the speed ratio of the toroidal continuously variable transmission to gradually vary towards a predetermined target speed ratio when the ignition switch is in the starting position and the speed ratio is smaller than the predetermined speed ratio range.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.